As TFT technology used for liquid crystal displays progresses, and the information infrastructure expands these days, various kinds of flat panel detectors (to be referred to as “FPDs” hereinafter) have been proposed, and achieved a large screen size and digitization even in the field of medical imaging.
The FPD can instantaneously read out a radiation image and display it on a display screen. The FPD can also directly extract an image as digital information. This enables convenient data handling, i.e., facilitates saving, manipulation, and transmission of data. It has been confirmed that characteristics such as sensitivity are equal to or greater than those of conventional screen film imaging and computed radiography, though the characteristics depend on the imaging conditions.
Japanese Patent Laid-Open No. 2002-40144 discloses a photoelectric conversion apparatus with a light source. This apparatus improves usability by suppressing a characteristic variation in extended use and decreases S/N ratio caused by a dark current and shortens the imaging cycle by using the light source.
U.S. Pat. No. 5,905,772 and Japanese Patent Laid-Open No. 2004-33659 disclose an X-ray detection apparatus with a light source.
Japanese Patent Laid-Open No. 2004-146769 discloses attaching a light guiding layer to a back surface of a TFT substrate by means of, e.g., a transparent adhesive.
Japanese Patent Laid-Open No. 2005-308440 discloses an electromagnetic shield that covers the periphery of a light irradiation means. Japanese Patent Laid-Open No. 2005-308440 also discloses storing an illuminous body and a lighting circuit in the light irradiation means.
The above-mentioned patent references, however, do not disclose a method of optimizing a mounting position and a mounting method of the light source. In the prior art, the light source and a driving circuit of driving source thereof are arranged near a readout circuit to read out an image signal, and a signal wire of the readout circuit. Heat, the driving signal itself, and vibrations from the light source of driving circuit thereof may generate noise in the image signal. There is a need for measures against this problem.